Removal of niobium second phase particle deposits from pickled zirconium-niobium alloys
View Patent ↗The present invention relates generally to a process and chemical composition for the removal of adherent niobium-rich second-phase particles (SPPs) from pickled niobium-containing zirconium alloys which includes applying to the alloy surface a chemical composition comprising alkaline hydrogen peroxide; an alkali metal meta-silicate; and a magnesium salt.
1. A process for removing adherent niobium-rich second phase-particle (SPP) deposits from a surface of a pickled zirconium-niobium alloy, comprising the step of:
applying to the surface a chemical composition which comprises: alkaline hydrogen peroxide; an alkali metal meta-silicate; and a magnesium salt,
wherein said applying step removes said niobium-rich second phase-particle (SPP) deposits from the surface of pickled zirconium-niobium alloy.
2. The process of claim 1 wherein applying the chemical composition comprises dipping the alloy into a bath containing the chemical composition.
3. The process of claim 1 wherein the hydrogen peroxide is present in an amount of 3 to 30 weight percent based on total weight of the composition.
4. The process of claim 1 wherein the alkali metal meta-silicate is selected from the group consisting of sodium meta-silicate and potassium meta-silicate.
5. The process of claim 1 wherein the alkali metal meta-silicate is sodium meta-silicate.
6. The process of claim 1 wherein the magnesium salt is present in an amount of at least 0.04 weight percent based on total weight of the composition.
7. The process of claim 1 wherein the magnesium salt is selected from the group consisting of magnesium sulfate and magnesium nitrate.
8. The process of claim 1 , wherein the magnesium salt is magnesium sulfate.
9. The process of claim 1 wherein the magnesium salt is present in an amount of from 0.2 to 1.0 weight percent based on total weight of the composition.
10. The process of claim 1 wherein applying the chemical composition is carried out at ambient temperature.
11. The process of claim 1 further comprising rinsing the alloy following applying the chemical composition to the surface of the alloy.
12. The process of claim 1 wherein the chemical composition has a pH of from 10.0 to 10.7.
13. The process of claim 1 wherein the chemical composition is in a form of a gel.
14. The process of claim 5 wherein the sodium meta-silicate is present in an amount of from 2 to 12 weight percent based on total weight of the composition.